Dam, Attics & Knees

March 28, 2017

At Infrared Diagnostic, we are often called to houses where there’s a kneewall attic. This is often a living space built into a sloped roof area. It can be a bonus room over a garage in a new house, or a walk-up attic in an older house. It’s called a ‘kneewall’ because of the short wall that is set in from the eaves of the roof. This kneewall ties into the attic floor and the sloped roof and might have storage behind it.

The kneewall typically separates the conditioned space from the unconditioned space. Since this boundary can be leaky, it can be the source of a lot of comfort problems, meaning your bonus room can end up being too hot in the summer and too cold in the winter.

A kneewall attic leads to all sorts of challenges for air sealing and insulation. When these two energy conservation measures are missing, or are not done properly, the kneewall attic can be a large source of of air leakage, which can lead to moisture problems inside the house and ice damming on the roof.

Why is a Kneewall Attic Challenging?

When you are carrying out air sealing work, which is your first line of defense against moisture problems and ice dams, you really need to pay attention to the way the attic is constructed. The kneewall creates several different surfaces and connection points that can be tricky to air seal and insulate properly. Here are a few problems that can happen that directly affect your comfort:

The floor joists that the kneewall sits on don’t have any blocking or air sealing, allowing outside air to overheat or cool the floor of the attic (and the living space below, as well).

Fiberglass batt insulation is not often installed properly (in complete contact with the the backside of the drywall).

Batt insulation without attic-side air barrier or sheathing is likely to fall out of the kneewall cavity and does not provide adequate air sealing and thermal performance of the installed insulation.

Batt insulation does not stop air movement, so without proper air sealing at places like access doors and electrical outlets, you will end up using more energy than necessary with more energy use than you should have in both heating and cooling seasons.

Fixing these problems has to be done in the right order, or you’ll cause more problems!

What Our Customers Are Saying

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Marcia, Worcester, MA

Had Flemming do the energy inspection on our 130+ year old house. He did a wonderful job explaining what he found telling me about what he would suggest. When we remodeled a year or so later we incorporated many of his recommendations into the work.

Mike, Arlington, MA

This is an excellent vendor. Flemming was punctual, professional and very thorough. He returns calls, arrives at the job promptly, and he did an excellent job evaluating my home.

Matt, Cambridge, MA

We had first had the Massachusetts "MassSave" free energy audit performed, and that turned out to be underwhelming. They identified little specific in our 80+ yr old house, and the only benefit was they swapped for free incandescent lightbulbs with compact fluorescents.

Orest, Brookline

Flemming Lund performed an infrared audit of my home. He provided a detail report with color photos and recommendations. The report provided was extremely detailed and it ended up being invaluable for the insulation work I ended up doing with another vendor.

Kathleen, Weston

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Lori, Arlington

Flemming Lund at Infrared Diagnostic was extremely helpful identifying the root causes for a number of long-standing issues with my house. He promptly produced report that will be very helpful for both fixing the problems as well as for saving energy. Thank you again!

We got the report last night. Thanks for sending it so quickly. Again, I cannot tell you how exciting it was to see all the data you generated for us and how grateful I was for the bits of knowledge you provided; all that is going to be very helpful as the guys start work on the house.